Bifurcated biological pulmonary valved conduit

ABSTRACT

The present invention comprises a pulmonary valved conduit that permits inflow diameters greater than about 22 mm while still maintaining the advantages of a naturally-formed biological valved conduit. Specifically, the present invention comprises a valved vascular prosthetic having an inflow conduit comprising a manifold formed from the sealed attachment of at least two venous valvular conduits.

This is a continuation of U.S. patent application Ser. No. 09/252,333,filed Feb. 18, 1999, now U.S. Pat. No. 6,110,201.

BACKGROUND OF THE INVENTION

Pulmonary valved conduits, used to replace diseased arteries such as thepulmonary artery, have been used for the last thirty years. Thesepulmonary valved conduits have been generally effective at treatingpulmonary atresia, pulmonary stenosis, or pulmonary insufficiency. Inearly embodiments, the conduits consisted of crimped woven or knitpolyester tubes housing a valve fabricated from metal components ormetal/plastic polymer components. Later valves consisted of metal framessuspending ceramic flat or curved (convex or concave) discs or hemidiscsthat were passive to the flow of blood exiting the chambers of theheart.

There were at least two disadvantages of these pulmonary valvedconduits. First, there was a need to preclot the polyester tubes inorder to preclude blood from seeping through the pores of the knit orwoven material. Second, after months of usage, a layer of fibrinousmaterial formed in the inner lumen over time from the accumulation ofblood proteins. This layer of fibrinous material, referred to as“intimal peel,” often separated from the inner wall and interfered withthe effective operation of the valve. An ineffective valve requiredre-operation to replace the conduit and valve, if caught in time. Insome instances, if valve replacement came too late, the results werefatal.

In the case of a mechanical valve made of metals and ceramics, there wasalso the need to continuously medicate the patient with anticoagulantsfor the duration of his life. That is because no man-made material thatis impervious to the clotting effects of blood exists today.Anticoagulation of the patient prevents coagulation of blood on thesurfaces of the inner lumen and on the sinuses of the cusps of thevalves. Moreover, for children suffering from congenital pulmonaryatresia or pulmonary insufficiency, the use of pulmonary valved conduitswere not always effective. As the child grew, the prosthetic was lesseffective due to its inadequate size, requiring frequent replacement.Also, for children especially, anticoagulation requirements aredifficult to regiment.

Beginning in the early 1970s, biological valves were used within thecrimped polyester conduits to produce a hybrid prosthetic referred to asa biological valved conduit. It was believed that a biological valve,such as a porcine aortic valve fixed with formaldehyde orglutaraldehyde, would eliminate the need for lifetime anticoagulationadministration. While the desired result was achieved, there was stillthe problem of separation of the “intimal peel” from the inner lumen.The intimal peel clogged the leaflets of the biological valve. Moreover,while a porcine aortic valve functioned relatively well as a replacementaortic valve, where the blood pressures from the left ventricle aresubstantially high (80–120 mmHg), it did not function nearly aseffective as a replacement pulmonary valve, where the blood pressuresfrom the right ventricle are quite low (0–15 mmHg). The porcine aorticvalve leaflets, which are relatively thick, become substantially lessflexible when “fixed” by chemical solutions. Opening at low pressuresbecomes more difficult. Also, the flow therethrough becomes turbulent,which undesirably promotes the degeneration of the biological material.

The disadvantages mentioned above can be minimized or overcome by usinga naturally formed biological conduit which integrates a valve suitablefor pulmonary replacement. Preferably, the valve opens and remains openwith minimal resistance to the flow of blood at relatively low pressuresof less than 1 mm Hg. The valve should also preferably close under theeffect of minimal backflow of blood and be capable of withstandingbackflow pressures of up to 200–300 mm Hg. An example of anaturally-formed valvular conduit is described in U.S. Pat. No.5,500,014 to Quijano, et al., the entire specification of which isincorporated herein by reference.

Even this arrangement is limited in that the naturally formed donorconduits have normally minimum diameters of about 22 mm. The largestnaturally occurring biological valved conduits are veins with venousvalves found in the jugular veins of caprine, cervine, canine, ovine,bovine, equine and other quadruped species and marsupials (e.g.,kangaroos and wallabies). While children may be treated effectively withpulmonary valved conduits having such diameters of 22 mm or less, manyadolescents and adults require larger-diameter prosthetics. The flowcapacity of a pulmonary conduit exiting the right ventricle must belarge enough to permit oxygenation of the blood at a sufficient rate tomaintain systemic perfusion with blood returning to the heart from thelungs. With normal pulmonary circulation, the blood exiting the rightheart through the pulmonary artery (trunk) divides into two separateflows: the right pulmonary artery servicing the right lung, and the leftpulmonary artery servicing the left lung. That requires that each lungreceive enough flow of blood through each of the two pulmonary arteriesemanating from the pulmonary trunk. That flow capacity often requires adiameter greater than the 22 mm found in the jugular veins of donoranimals.

SUMMARY OF THE INVENTION

The present invention comprises a pulmonary valved conduit that permitsinflow diameters greater than about 22 mm while still maintaining theadvantages of a naturally-formed biological valved conduit.Specifically, the present invention comprises a vascular prostheticsuitable for replacing a patient's damaged or missing pulmonary valve,said prosthetic comprising an inflow conduit comprising a manifoldformed from the sealed attachment of a plurality of donor valved bloodvessels, each of said blood vessels housing a biological valve integraltherewith, said blood vessels configured to permit the flow of bloodtherethrough by the valve opening at a relatively low pressure andconfigured to prevent the backflow of blood therethrough by the valveclosing so as to withstand relatively high pressures, said manifoldformed upstream of each of the biological valves so as not to interferewith the effective operation of the biological valves, said inflowconduit having a resulting flow capacity following sealed attachmentthat is larger than the original flow capacity of each of the donorblood vessels, said prosthetic also comprising an outflow conduitpositioned downstream of each of the biological valves.

The present invention prosthetic is prepared by using two approximatelyequal sized (diameter) jugular valved veins obtained from one of thequadrupeds identified above and attaching them in such a fashion toprovide a resulting inflow area larger than each of the original donorveins. The inventive manifold does not alter or disturb theconfiguration of the valve itself. In the preferred embodiment, abifurcated device is created wherein each of the branches includes itsown biological valve flow. Various means of attachment can be used, suchas stitching with medical surgical suture, or by means of proteinsealants, glues, collages or laser radiation beams. Moreover, theattachment is preferably made so as to minimize the angle of transitionof the blood running through the conduit at the site of the bifurcation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of a venous valvular conduit, showing thevalve leaflets in an open position.

FIG. 2 is a perspective of two section of venous valvular conduits,indicating where a proposed slicing of the conduits is to be made.

FIG. 3 is a perspective of the two section of venous valvular conduitsof FIG. 2, indicating where the slices of the conduits have been made inpreparation for attachment.

FIG. 4 is a perspective view of the preferred embodiment of the presentinvention showing how the two venous valved conduits of FIG. 2 have beenjoined.

FIG. 5 is a perspective view of a variation of the embodiment of FIG. 4showing a unitary outflow end.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIG. 1, the present invention improves upon the use ofa naturally-formed venous valvular conduit 10 consisting of a bloodvessel 12 housing a biological valve 14. The valve 14 consists of aplurality of leaflets 16 (two shown) that easily open upon the flow oflow pressure blood 18, but closely tightly against a relatively lowbackpressure of blood; remaining sealed even against backpressures ashigh as 200–300 mmHg. Such venous valvular conduits may be found, asindicated above, in one of many quadrupeds. Preferably, the donor venousvalvular conduit is a section of the jugular vein of a quadruped, thediameters of which approach about 22 mm. While humans havenaturally-formed venous valvular conduits, none approach that diameter.

With reference to FIGS. 2–4, the present invention comprises a method ofmaking a vascular prosthetic comprising a valvular conduit suitable forpulmonary valve replacement, wherein the conduit has a diameter greaterthan 22 mm. The flow output of many human adult right ventriclesrequires that a pulmonary valve prosthetic have diameters greater than22 mm to maximize the effectiveness of the prosthetic.

With specific reference to FIG. 2, the present invention maximizes thatbenefit by inventively combining two generally-equally-sized donorvalvular conduits 20, 30, each having a biological valve 22, 32 housedtherewithin. Each conduit 20, 30 has an inflow end 24, 34 and an outflowend 26, 36. The donor valvular conduits are preferably fixed toeffectively preserve the conduits in an aldehyde solution; preferablyglutaraldehyde, or any other similar solution such as formaldehyde. Thatentails, for example, soaking the tissue in the aldehyde solution orpassing the solution through the valved conduit while immersing theconduit in said solution. Other types of fixation include gammaradiation and polyepoxy compounds. In the preferred embodiment, a sliceof the conduits 20, 30 is made where indicated at 28, 38.

Referring to FIG. 3, the slicing of each conduit 20, 30 results in anangular sectioned inflow end 24, 34 configured to be joined in a mannershown in FIG. 4. As shown in FIG. 4, the resulting vascular prosthetic50 comprises an inflow end manifold 52 having a diameter D2. Where thediameter of each donor conduit is D1, the diameter D2 of the resultingprosthetic conduit inflow end manifold 52 is greater than D1. Where itis desired to have a vascular prosthetic with an inflow end diametergreater than 22 mm, the preferred embodiment of the present methodcomprises attaching two donor valvular conduits having diameterssubstantially less than about 22 mm in the manner shown in FIGS. 2 and3. The resulting diameter D2 will be greater than 22 mm.

As shown in FIG. 4, the present invention prosthetic 50 comprises theinflow end manifold 52 having a seam 54 upstream of the two donorbiological valves 22, 32. Preferably, to minimize the angle oftransition for the blood flow 56, the slice cut from the two donorconduits 20, 30 is made at an angle (θ1) of less than about 15°,although other angles may be appropriate. The resulting angle (θ2) ofthe vascular prosthetic is, therefore, preferably less than 30°,although other angles may be appropriate. Where desired, the resultingprosthetic itself may be preserved via chemical fixation or other typeof fixation.

It is contemplated that the attachment of sectioned donor conduits 20,30 be made via a plurality of stitches made in one or more passes.Preferably, a single pass of stitches is made on the interior tomaintain as smooth an inner lumen as possible. Furthermore, it ispreferable that each stitch be applied in a manner that said stitcheswill not unravel when tissue and included neighboring stitches aresevered. Discrete stitches may be used. Externally, at least one pass,but preferably two passes, of stitches is applied to reinforce theattachment. Other methods of attachment are also contemplated, includingbiological and chemical sealants, and laser beam radiation.

With the embodiment of FIG. 4, the inflow end 52 may be attacheddirectly to the right ventricle at our about the location of the inflowto the patient's pulmonary trunk. Each outflow end 26, 36 of theprosthetic may be attached to the left and right pulmonary arteries,respectively, thereby bypassing the patient's diseased or missingpulmonary valve. Alternatively, each outflow end 26, 36 could beattached to different locations of the downstream end of the patient'spulmonary trunk, if desired.

With reference to FIG. 5, a second embodiment 60 of the presentinvention is contemplated. The second embodiment 60 comprises an inflowend manifold 62 having a seam 64 and an outflow end manifold 66 having asecond seam 68. Where it is desired to have a prosthetic with a singleoutflow end, the present inventive method further comprises slicing theoutflow ends of two donor valvular conduits in the same or similarmanner as described above and shown in FIG. 3. Performing those steps,the outflow ends of the donor valvular conduits may be attached to formthe second outflow end manifold 66 wherein the resulting seam 68 isformed from a plurality of passes of stitches, as described above. Thissecond embodiment 60 may be attached at the inflow end to the rightventricle and at the outflow end to the pulmonary trunk, therebybypassing the patient's diseased or missing pulmonary valve.

1. A vascular prosthetic comprising: at least two chemically fixedbiological tissue valvular conduits, each of said conduits having anangular sectioned inflow end and an outflow end and a valve ofchemically fixed biological tissue housed therein; an inflow conduithaving a large diameter cross-sectional area and a smooth inner lumen; aseam, the seam comprising a plurality of single pass stitches, the seamon the angular sectioned inflow ends to attach the inflow ends to eachother to define the inflow conduit, the smooth inner lumen oriented atan angle of less than 30 degrees to each of the at least two valvularconduit outflow ends, the inflow conduit positioned upstream of each ofsaid valves.
 2. The vascular prosthetic of claim 1 wherein the inflowconduit is suitable for attachment to a heart to receive blood from theright ventricle.
 3. The vascular prosthetic of claim 1 wherein-at leastone outflow end is suitable for attachment to a pulmonary trunk.
 4. Thevascular prosthetic of claim 1 wherein the outflow ends are suitable forattachment to first and second pulmonary arteries.
 5. The vascularprosthetic of claim 1 wherein the valve of each valvular conduit opensat pressures as low as about 1 mm Hg and remains sealably closed so asto withstand backflow pressures greater than about 200 mm Hg.
 6. Thevascular prosthetic of claim 1 wherein the cross-sectional area of theinflow end of the vascular prosthetic is greater than about 22 mm. 7.The vascular prosthetic of claim 1 wherein the cross-sectional area ofthe inflow end of the prosthetic is greater than about 28 mm.
 8. Thevascular prosthetic of claim 1 wherein the fixed tissue conduits arefixed by an aldehyde.
 9. The vascular prosthetic of claim 1 wherein thefixed tissue conduits are fixed by a polyepoxy compound.
 10. A vascularprosthetic comprising: a “Y” shaped conduit of fixed biological tissuehaving a large diameter inflow conduit, a bifurcated outflow conduitcomprising two valvular conduit outflow ends and an integral valvedisposed in each valvular conduit outflow ends, the pulmonary valvedconduit formed from chemically fixed biological tissue, wherein each ofsaid valvular conduits ends is joined at a seam forming the inflowconduit, the seam including a plurality of stitches forming a smoothinner lumen along the large diameter inflow conduit, the smooth innerlumen in fluid communication across the integral valves with the flowpath in the valvular conduit outflow ends at an angle of −transitionless than 15 degrees from said inflow conduit to either of the valvularconduit outflow ends, the large diameter inflow conduit with across-sectional area larger than the cross-sectional area of either ofthe two valvular conduit outflow ends forming the “Y” shape.
 11. Thevascular prosthetic of claim 10 wherein the single inflow end issuitable for attachment to a heart to receive blood from the rightventricle.
 12. The vascular prosthetic of claim 10 wherein the valvularconduits comprise first and second outflow ends, wherein at least oneoutflow end is suitable for attachment to a pulmonary trunk.
 13. Thevascular prosthetic of claim 12 wherein the first and second outflowends are suitable for attachment to first and second pulmonary arteries.14. The vascular prosthetic of claim 10 wherein the valve of eachvalvular conduit opens at pressures as low as about 1 mm Hg and remainssealably closed so as to withstand backflow pressures greater than about200 mm Hg.
 15. The vascular prosthetic of claim 10 wherein thecross-sectional area of the inflow end of the vascular prosthetic isgreater than about 22 mm.
 16. The vascular prosthetic of claim 10wherein the cross-sectional area of the inflow end of the vascularprosthetic is greater than about 28 mm.
 17. The vascular prosthetic ofclaim 10 wherein the stitches are formed in a single pass.
 18. Thevascular prosthetic of claim 10 wherein the fixed tissue conduits arefixed by an aldehyde.
 19. The vascular prosthetic of claim 10 whereinthe fixed tissue conduits are fixed by a polyepoxy compound.
 20. Avascular prosthetic comprising: an inflow conduit comprising a manifoldformed from the attachment of two donor valved blood vessels, theattachment including a plurality of stitches forming a smooth innerlumen, each of said two blood vessels housing a biological valveintegral therewith, each blood vessel configured to permit the flow ofblood therethrough by the valve opening at a relatively low pressure andconfigured to prevent the backflow of blood therethrough by the valveclosing so as to withstand relatively high pressures, said manifoldformed at an angle of transition of the blood flow therethrough that isless than 30 degrees upstream of the biological valves so as not tointerfere with the effective operation of the biological valves, theinflow conduit with a cross-sectional area larger than thecross-sectional area of either of the inflow ends of each of the donorblood vessels, and an outflow conduit positioned downstream of each ofthe biological valves.
 21. The vascular prosthetic of claim 20 whereinthe inflow conduit is suitable for attachment to a heart to receiveblood from the right ventricle.
 22. The vascular prosthetic of claim 20wherein the donor blood vessels comprise first and second outflow ends,wherein at least one outflow end suitable for attachment to a pulmonarytrunk.
 23. The vascular prosthetic of claim 22 wherein the first andsecond outflow ends are suitable for attachment to first and secondpulmonary arteries.
 24. The vascular prosthetic of claim 20 wherein thevalve of each donor blood vessel opens at pressures as low as about 1 mmHg and remains sealably closed so as to withstand backflow pressuresgreater than about 200 mm Hg.
 25. The vascular prosthetic of claim 20wherein the cross-sectional area of the inflow conduit of the vascularprosthetic is greater than about 22 mm.
 26. The vascular prosthetic ofclaim 20 wherein the cross-sectional area of the inflow conduit of thevascular prosthetic is greater than about 28 mm.
 27. The vascularprosthetic of claim 20 wherein the plurality of donor blood vessels arechemically fixed biological tissue.
 28. The vascular prosthetic of claim27 wherein the plurality of donor blood vessels are fixed by analdehyde.
 29. The vascular prosthetic of claim 20 wherein the stitchesare formed in a single pass.
 30. The vascular prosthetic of claim 27wherein the plurality of donor blood vessels are fixed by a polyepoxycompound.
 31. The prosthetic of claim 20 wherein the plurality of donorblood vessels each comprise a vein segment.
 32. The prosthetic of claim31 wherein the plurality of donor blood vessels each comprise thejugular vein of a donor quadruped or marsupial.
 33. The prosthetic ofclaim 32 wherein the valved blood vessels each comprise the jugular veinof a donor caprine, cervine, canine, ovine, bovine, equine or marsupial.34. A vascular prosthetic comprising: two chemically fixed biologicaltissue valvular conduits, each of said conduits having an angularsectioned inflow end and an outflow end and a valve of chemically fixedbiological tissue housed therein, each of said conduits comprising thejugular vein of a donor quadruped or marsupial; wherein each of saidconduits is joined at the angular sectioned inflow ends by stitches toform a single inflow end having a smooth inner lumen with a singleinflow end cross-sectional area larger than the cross-sectional area ofany of the inflow ends of said valvular conduits, the joinder providingan angle of transition of the blood flow through the single inflow endand into the outflow ends that is less than 30 degrees.
 35. The vascularprosthetic of claim 34 wherein the single inflow end is suitable forattachment to a heart to receive blood from the right ventricle.
 36. Thevascular prosthetic of claim 34 wherein the valvular conduits comprisefirst and second outflow ends, wherein at least one outflow end issuitable for attachment to a pulmonary trunk.
 37. The vascularprosthetic of claim 34 wherein the valvular conduits comprise first andsecond outflow ends that are suitable for attachment to first and secondpulmonary arteries.
 38. The vascular prosthetic of claim 34 wherein thevalve of each valvular conduit opens at pressures as low as about 1 mmHg and remains sealably closed so as to withstand backflow pressuresgreater than about 200 mm Hg.
 39. The vascular prosthetic of claim 34wherein the cross-sectional area of the inflow end of the vascularprosthetic is greater than about 22 mm.
 40. The vascular prosthetic ofclaim 34 wherein the cross-sectional area of the inflow end of thevascular prosthetic is greater than about 28 mm.
 41. The vascularprosthetic of claim 34 wherein the fixed tissue conduits are fixed by analdehyde.
 42. The vascular prosthetic of claim 34 wherein the fixedtissue conduits are fixed by a polyepoxy compound.